Issue 4340 - Drop dependency on external xar tool

xarfile.py

Index: xarfile.py
===================================================================
new file mode 100644
--- /dev/null
+++ b/xarfile.py
@@ -0,0 +1,140 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import re
+import struct
+import time
+import zlib
+
+from Crypto.Hash import SHA
+from Crypto.PublicKey import RSA
+from Crypto.Signature import PKCS1_v1_5
+
+from buildtools.packager import getTemplate
+
+XAR_HEADER = struct.Struct('>IHHQQI')
+XAR_HEADER_MAGIC = 0x78617221
+XAR_VERSION = 1
+XAR_CKSUM_SHA1 = 1
+
+
+def read_certificates_and_key(keyfile):
+    with open(keyfile, 'r') as file:
+        data = file.read()
+
+    certificates = []
+    key = None
+    for match in re.finditer(r'-+BEGIN (.*?)-+(.*?)-+END \1-+', data, re.S):
+        section = match.group(1)
+        if section == 'CERTIFICATE':
+            certificates.append(re.sub(r'\s+', '', match.group(2)))
+        elif section == 'PRIVATE KEY':
+            key = RSA.importKey(match.group(0))
+    if not key:
+        raise Exception('Could not find private key in file')
+
+    return certificates, key
+
+
+def get_checksum(data):
+    return SHA.new(data).digest()
+
+
+def get_hexchecksum(data):
+    return SHA.new(data).hexdigest()
+
+
+def get_signature(key, data):
+    return PKCS1_v1_5.new(key).sign(SHA.new(data))
+
+
+def compress_files(filedata, root, offset):
+    compressed_data = []
+    filedata = sorted(filedata.iteritems())
+    directory_stack = [('', root)]
+    file_id = 1
+    for path, data in filedata:
+        # Remove directories that are done
+        while not path.startswith(directory_stack[-1][0]):
+            directory_stack.pop()
+
+        # Add new directories
+        directory_path = directory_stack[-1][0]
+        relpath = path[len(directory_path):]
+        while '/' in relpath:
+            name, relpath = relpath.split('/', 1)
+            directory_path += name + '/'
+            directory = {
+                'id': file_id,
+                'name': name,
+                'type': 'directory',
+                'mode': '0755',
+                'children': [],
+            }
+            file_id += 1
+            directory_stack[-1][1].append(directory)
+            directory_stack.append((directory_path, directory['children']))
+
+        # Add the actual file
+        compressed = zlib.compress(data, 9)
+        file = {
+            'id': file_id,
+            'name': relpath,
+            'type': 'file',
+            'mode': '0644',
+            'checksum_uncompressed': get_hexchecksum(data),
+            'size_uncompressed': len(data),
+            'checksum_compressed': get_hexchecksum(compressed),
+            'size_compressed': len(compressed),
+            'offset': offset,
+        }
+        file_id += 1
+        offset += len(compressed)
+        directory_stack[-1][1].append(file)
+        compressed_data.append(compressed)
+    return compressed_data
+
+
+def create(archivepath, contents, keyfile):
+    certificates, key = read_certificates_and_key(keyfile)
+    checksum_length = len(get_checksum(''))
+    params = {
+        'certificates': certificates,
+
+        # Timestamp epoch starts at 2001-01-01T00:00:00.000Z
+        'timestamp_numerical': time.time() - 978307200,
+        'timestamp_iso': time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime()),
+
+        'checksum': {
+            'offset': 0,
+            'size': checksum_length,
+        },
+        'signature': {
+            'offset': checksum_length,
+            'size': len(get_signature(key, '')),
+        },
+        'files': [],
+    }
+
+    offset = params['signature']['offset'] + params['signature']['size']
+    compressed_data = compress_files(contents, params['files'], offset)
+
+    template = getTemplate('xartoc.xml.tmpl', autoEscape=True)
+    toc_uncompressed = template.render(params).encode('utf-8')
+    toc_compressed = zlib.compress(toc_uncompressed, 9)
+
+    with open(archivepath, 'wb') as file:
+        # The file starts with a minimalistic header
+        file.write(XAR_HEADER.pack(XAR_HEADER_MAGIC, XAR_HEADER.size,
+                                   XAR_VERSION, len(toc_compressed),
+                                   len(toc_uncompressed), XAR_CKSUM_SHA1))
+
+        # It's followed up with a compressed XML table of contents
+        file.write(toc_compressed)
+
+        # Now the actual data, all the offsets are in the table of contents
+        file.write(get_checksum(toc_compressed))
+        file.write(get_signature(key, toc_compressed))
+        for blob in compressed_data:
+            file.write(blob)